1. Field of the Invention
The invention relates to a device for making holes for the implantation of interlocking bone nails.
2. Description of the Prior Art
Interlocking nails are used for bone fractures and have transverse bores for fixation within the bone by bone screws. Such a nail is shown in U.S. Pat. No. 4,976,258. The screws secure the nail against relative axial and rotational movement. The interlocking nails are inserted proximally, for example in the femur, and the distal portion of the nail normally has two transverse bores so that aligned bores or holes must be made in the conical bone. The correct positioning of the transverse bores within the bone is relatively difficult and requires additional instrumentation. For this purpose, targeting devices are used in combination with an X-ray source and an X-ray image converter.
Manually operable unsupported targeting devices are known as well as devices attached to a relatively stationary targeting system. The direct attachment of the targeting device to an image converter enables an accurate placement of the holes. A displacement of the leg of a patient or of the surgical table causes a misalignment.
The German Gebrauchsmuster 84 17 428 (U.S. Pat. Nos. 4,625,718 and 4,850,344) discloses an apparatus which combines a targeting device with a power-driven drilling tool in that a radiation transparent chuck is used. The drill bit is projected as a spot if it is extended parallel to the radiation direction.
The EP-A-O 201 737 discloses a targeting device including a drill sleeve connected to a handle and a sighting device connected to the sleeve, with the position of the sighting device between a radiation source and a radiation receiver made visible through an image converter. A sighting device separate from the drilling sleeve has the advantage that the control and correction of the targeting device can be carried out during the drilling process. However, it is disadvantageous that a target element must be attached to the drilling sleeve prior to the detection of the drilling axis by means of the sighting device. A target element may consist of a radiation transparent pin having a radiation-impervious spot at the tip. By using the sighting means and the target pin, the drill sleeve can be accurately positioned against the bone. After repeated alignments with the sighting device, the hole is made by guiding the drill bit in the drilling sleeve.
The German Gebrauchsmuster 87 03 438 discloses an auxiliary instrument for the setting of holes wherein a guiding member is attached to a handle and is made of a material transparent for X-rays. The guiding member includes a guiding bore for the slidable guidance of a rod-shaped punching tool. The guiding member includes two axially spaced annular members encircling the guiding bore which appear in an overlapped formation on the screen if the X-rays are aligned with the guiding bore.
The described manually operable devices require a permanent correction of the position of the drilling sleeve during the drilling process in order to insure that both the first and second bores in the cortical bone are accurately positioned. This correction is made by the X-ray device. Examples of related targeting devices are described in U.S. Pat. Nos. 4,917,111, 5,013,317 and 5,030,222.